Oct. 24 (HealthDay News) -- Anxiety disorders are linked to a number of physical problems, including arthritis, migraine headaches, respiratory disease, gastrointestinal issues, allergies, and thyroid disease, a new study finds.

Experts have long recognized an association between depression and physical illness, while evidence of a link between anxiety and physical health is more recent, according to background information in the article.

In this study, Canadian researchers analyzed data on nearly 4,200 people who took part in the German Health Survey between 1997 and 1999. The participants had a physical examination and filled out a questionnaire that asked them about 44 specific health conditions. They also filled out a quality of life survey that measured factors such as physical functioning, pain, and general health.

The participants also underwent psychiatric interviews designed to detect anxiety disorders, such as panic disorder, social phobia, obsessive-compulsive disorder, and agoraphobia (fear of being in a situation where anxiety or panic may occur and it may be difficult to escape from the situation).

Of the study participants, 8.4 percent had had an anxiety disorder within the previous month and 60.8 percent had had a physical problem. The researchers found that having an anxiety disorder was associated with having any type of physical condition.

Most people with both an anxiety disorder and a physical problem developed the anxiety disorder first and they tended to have a poorer quality of life than people with either an anxiety disorder or physical condition alone.

"The mechanisms of association between anxiety disorders and physical conditions remain unknown, although several possibilities should be considered," the study authors wrote in the Oct. 23 issue of the journal Archives of Internal Medicine.

For example, having a physical illness may cause worry and anxiety that eventually becomes serious enough to qualify as an anxiety disorder; having an anxiety disorder may trigger biological changes that contribute to physical illness; or a third condition, such as a substance abuse disorder, could be linked with both anxiety disorder and physical illness.

"Although there have been increased efforts to recognize and treat depression in the medically ill, our findings underscore the need to create similar programs to recognize and treat anxiety disorders in the medically ill," the authors wrote.

SOURCE: JAMA/Archives journals, news release, Oct. 23, 2006